Conventionally, as solid electrolytic capacitors, a resin mold sealed type solid electrolytic capacitor in which a capacitor element is sealed by molding or a box sealed type solid electrolytic capacitor in which a capacitor element is sealed by a box-shaped case are well known.
For example, as shown in Patent Document 1 listed below, in the box sealed type solid electrolytic capacitor, in a state in which a capacitor element is accommodated inside a case main body having a bottom wall and peripheral side walls provided at peripheral four sides (outer peripheral edge portions) of the bottom wall, an upper opening of the case main body is closed in a sealed manner by an upper lid.